The present invention relates generally to communication systems. The present invention relates more particularly to bit-rate sampled data transmission, such as telephone, fax or modem communication utilizing a cable modem/cable modem termination system.
A desired solution for high speed data communications appears to be cable modem. Cable modems are capable of providing data rates as high as 56 Mbps, and is thus suitable for high speed file transfer, including applications such as bit-rate sampled data transmission to and from telephones, faxes or modem devices.
However, when transmitting packet based voice using cable modems, there is a need to synchronize voice packet sampling with cable modem system grant processing. The present invention provides a solution for such need.
In accordance with the present invention a method of processing sampled voice packets from a voice packet sender for transmission over a bit-rate sampled data transmission system, such as by a cable modem over a cable modem termination system, to a voice packet recipient is provided. Unsolicited grant arrivals in response to a request from the voice packet sender coupled to the cable modem are determined. The storing of sampled voice packets is synchronized with the unsolicited grant arrivals. Upon receipt of an unsolicited grant arrival, currently stored sampled voice packets are transmitted to the cable modem for further transmission to the voice packet recipient over the cable modem termination system. The synchronization includes determining time needed between adjacent unsolicited grant arrivals for storing the sampled voice packets and for processing stored sampled voice packets, sampling voice packets by clocking voice packet sampling using a clock derived from a cable modem clock, and scheduling processing of the stored sample voice packets to be ready for transmission at a next unsolicited grant arrival. The time needed determination involves counting time between unsolicited grant arrivals and upon reaching a count indicative of the interval between unsolicited grant arrivals, providing for transmission of the currently stored sampled voice packets at the next unsolicited grant arrival.
Further, the voice packet recipient can be a Public Switched Telephone Network (PSTN) gateway a clock of a cable modem termination system is synchronized with a clock of the PSTN. Also, the processing of the sampled voice packets can be for voice compression.
In addition, the voice packet sender can include a plurality of voice packet senders, each voice packet sender having a channel identifier. A multiplexing transmission is provided based upon the channel identifier such that upon receipt of an unsolicited grant arrival associated with the channel identifier currently stored sampled voice packets of the voice packet sender identified by the channel identifier are transmitted to the cable modem for further transmission over the cable modem termination system to the voice packet recipient of the voice packet sender having the channel identifier.
In accordance with an embodiment of the present invention a method for communicating information is provided. A time slot is allocated in a time division multiple access system for a transmission from a subscriber to a headend, the time slot being sufficient for only a first portion of a transmission, a second portion of the transmission being transmitted in other than the first time slot. Synchronization of a clock of the subscriber with respect to a clock of the headend is enhanced using a message transmitted from the headend to the subscriber which is indicative of an error in a subscriber transmission time with respect to the time slot. A feedback loop process is used to determine at least one of fractional symbol timing correction and carrier phase correction of a transmission from the subscriber to the headend. The quality of at least one channel is monitored and modulation is changed in response changes to monitored channel quality. Information representative of parameters of received time division multiple access data is used to facilitate processing of the received time division multiple access data in a receiver, the parameters being communicated within the headend. Filter coefficients are generated at the headend from a ranging signal transmitted from the subscriber to the headend and transmitting the filter coefficients from the headend to the subscriber, the filter coefficients being used of the subscriber to compensate for noise in a transmission from the subscriber to the headend. Sampled packets from a packet sender are processed for transmission over a transmission system having a periodically allocated bandwidth to a packet recipient by: determining unsolicited grant arrivals in response to a request from the packet sender; synchronizing the storing of sampled packets with the unsolicited grant arrivals; and transmitting, upon receipt of an unsolicited grant arrival, currently stored sampled packets for further transmission to the packet recipient over the transmission system having a periodically allocated bandwidth.